1. Field of the Invention
This invention relates to a rotary, flat metallic fluid-tight and thrust-resisting seal and to a method of manufacturing such a seal.
2. Summary of the Prior Art
It is necessary in certain machines such as pumps, to provide fluid-tight axial thrust seals for a rotary shaft.
It is not known at the present time how to produce a rotary, flat, seal capable of simultaneously ensuring fluid-tightness in an efficient manner and resisting, over a long period, heavy loads. In order to provide for fluid-tightness, it is possible to imagine that the seal is constituted by two annular plane smooth faces one applied against the other. However, under the action of the axial load and of the rotation in the absence of lubrication, this would give rise to heating up which would rapidly lead to deterioration of the contacting members. It is therefore essential to lubricate the contact surfaces by causing the circulation of ambient fluid under pressure between the two faces. If the two faces are perfectly polished, fluid cannot circulate correctly and friction will be generated. Since it is necessary to have in this location between the faces a fluid film, it is necessary to machine at least one of the two faces so that it maintains the traces of the machining which are able to distribute the fluid over the whole surface. Unfortunately, known machining methods (cylindrical face grinding) leave the surface in a condition which will certainly result in good lubrication but also ambient fluid flow which is uncontrollable and is often excessive.
It is for this reason, in present day practice, that generally the functions of resistance to thrust loads and of fluid-tightness are provided separately, as follows. A lubricated thrust bearing which is not fluid-tight (with faces machined traditionally) is followed by a fluid-tight seal having no load of consequence to resist and made by means of two plane and lapped surfaces, the one of steel, the other of graphite, for example.
An object of the invention is to provide a rotary flat seal serving simultaneously the two functions of fluid-tight and of thrust resistance without giving rise to the disadvantages referred to.